VIEWS OF A. R. WALLACE 389 



indefinitely from the Original Type." The following quotations 

 will serve to show that his views on Natural Selection were closely 

 similar to those of Charles Darwin. 



" The life of wild animals is a struggle for existence. The 

 full exertion of all their faculties and all their energies is 

 required to preserve their own existence and provide for that of 

 their infant offspring. The possibility of procuring food during 

 the least favourable seasons, and of escaping the attacks of their 

 most dangerous enemies, are the primary conditions which 

 determine the existence both of individuals and of entire 

 species." 



" Even the least prolific of animals would increase rapidly if 

 unchecked, whereas it is evident that the animal population of 

 the globe must be stationary, or perhaps, through the influence 

 of man, decreasing. Fluctuations there may be ; but permanent 

 increase, except in restricted localities, is almost impossible. 

 For example, our own observation must convince us that birds 

 do not go on increasing every year in a geometrical ratio, as 

 they would do, were there not some powerful check to their 

 natural increase. Very few birds produce less than two young 

 ones each year, while many have six, eight, or ten ; four will 

 certainly be below the average ; and if we suppose that each pair 

 produce young only four times in their life, that will also be below 

 the average, supposing them not to die either by violence or want 

 of food. Yet at this rate how tremendous would be the increase 

 in a few years from a single pair ! A simple calculation will 

 show that in fifteen years each pair of birds would have increased 

 to nearly ten millions ! Whereas we have no reason to believe 

 that the number of the birds of any country increases at all in 

 fifteen or in one hundred and fifty years. With such powers of 

 increase the population must have reached its limits, and have 

 become stationary, in a very few years after the origin of each 

 species. It is evident, therefore, that each year an immense 

 number of birds must perish as many in fact as are born. . . . 

 It is, as we commenced by remarking, ' a struggle for existence,' 

 in which the weakest and least perfectly organized must always 

 succumb. 



" Now it is clear that what takes place among the individuals 

 of a species must also occur among the several allied species of 

 a group, viz., that those which are best adapted to obtain a 

 regular supply of food, and to defend themselves against the 

 attacks of their enemies and the vicissitudes of the seasons, must 

 necessarily obtain and preserve a superiority in population ; 

 while those species which from some defect of power or organization 

 are the least capable of counteracting the vicissitudes of food 



